Back in 1839, a 19-year-old Edmond Becquerel tinkering in his father’s laboratory discovered the photovoltaic effect: the principle that enables sunlight to be converted into electricity. It took well over a century before it was put to practical use. In the 1950s, Bell Laboratories developed solar panels to power space activities. But the electricity generated by those early photovoltaics was astronomically expensive, due to their inefficiency.
Today you can expect to pay £800 for a 350W panel (coming in at little more than £2 per watt), making them accessible to anyone with a roof and some disposable income. While Bell’s first practical cell converted just 6 per cent of sunlight into electricity, today’s commercial rooftop panels – built from wafers of crystalline silicon semiconductor – achieve over 20 per cent efficiency. Earlier this year Oxford PV set a new world record for commercial-sized panels of over 28 per cent.
However, this is about as good as silicon panels can get, in part because they are only able to convert narrow wavelengths of light into electricity. So for further significant improvements to be made, new technologies are required.
One of the most promising of these makes use of a calcium/titanium mineral called perovskite. Perovskite absorbs different wavelengths of light than silicon, so by combining the two materials, much more efficient panels are possible.
This is exactly what has been described in two papers published in Science this July. One team, headed by Prof Steve Albrecht from the Helmholtz Center Berlin for Materials and Energy in Germany, described efficiencies of 32.5 per cent for their silicon-perovskite cells. Another, led by Dr Xin Yu Chin at the Federal Institute of Technology in Lausanne, Switzerland, showcased an efficiency of 31.25 per cent.
Chin also stated that these new “tandem” cells held the promise of being both highly efficient and cost-effective to produce. Given that the sun is a truly renewable energy source, the benefits of cheaply harnessing its power are as clear as daylight.
This article is from New Humanist's autumn 2023 issue. Subscribe now.
